Conventionally, phase-change type optical information recording media have been known. In these phase-change type optical information recording media, a single laser beam is irradiated on a recording layer whereby the material of the recording medium undergoes crystalline-amorphous phase transition or crystalline-crystalline phase transition. This crystalline-amorphous phase transition or crystalline-crystalline phase transition is utilized to record, reproduce, or erase information repeatedly. Since overwriting of information can be conveniently performed with a single laser beam, development of this medium has been active lately.
Moreover, in recent years, computers are becoming faster and faster. Furthermore, amount of data handled by the computers are increasing day by day. To cope-up with the computers, the disk driving units which can perform recording, reproduction, or erasing of information at high-speed have been developed. However, still there are disk driving units those work at lower-speeds. Therefore, if same optical information recording media is to be used on variety of disk driving units, it is desirable that the optical information recording media have such recording and reproducing characteristics that they can be used at a wide speed range from the low to high speeds.
In case of the conventional phase-change type optical information recording medium, the recording and reproducing characteristics are optimized in such a manner that high degree of modulation can be obtained and the generated jitter is low even at high linear velocity, as well as generated jitter is low even after repetitive recording. However, if the characteristics of the phase-change type optical information recording medium are optimized in this manner, then there is a tendency that the characteristics of the recording signal at low linear velocity and after repetitive recording disadvantageously degrades.